In the related arts, in the case of scanning a document and storing as electronic data, there are: a line scanner using a line sensor for image pickup; and a camera scanner using a 2-dimensional imaging sensor. Particularly, in the case of the camera scanner in which a camera is disposed over a stage (or a bookrest) and an original is put onto the stage in a face-up state and is photographed, so long as a sheet of original, merely by putting the original, it can be soon scanned, and even a thick original such as a book can be easily put onto the stage and can be scanned. Further, a camera scanner in which not only a document such as paper or book but also a solid object is put onto a stage and a solid shape is scanned has been disclosed in PTL 1. According to the camera scanner disclosed in PTL 1, a light projecting unit is provided together with a camera for image pickup, a measurement pattern which is projected from the light projecting unit is photographed by the camera, and a solid shape is measured by a principle of triangular surveying. According to the camera scanner, the solid shape of the object put on the stage is calculated, whether it is a flat original, a book, or a solid object is discriminated, and the photographing is performed in a proper photographing mode in accordance with the discriminated object. According to a camera scanner disclosed in PTL 2, it has a similar construction, a measurement pattern is always projected by a light projecting unit from timing when no object is put on the stage, and the solid shape is continuously measured, thereby detecting that the object has been put on the stage.
On the other hand, according to a user interface system disclosed in PTL 3, a computer display screen is projected onto a desk by a projector and the computer display screen is operated with a fingertip. An infrared camera is used to detect a fingertip. According to the above user interface system, by reading a bar code printed on a paper document, a book, or the like on the desk, a link with electronic information can be generated.